Adoptive immunotherapy for metastatic cancer refers to the autologous or allogeneic transfer of immune cells capable of mediating an anti-tumor effect on tumor-bearing host. Tumor infiltrating T lymphocytes (TILs) are isolated from tumor tissue and characterized and expanded ex vivo and are re-infused into the cancer patients. Up to 109 activated cells are infused after a lymphodepleting regimen along with growth factors to augment the in vivo effects of transferred cells. In patients with advanced metastatic melanoma, refractory to other treatments, 50% have demonstrated an objective response according to the Response Evaluation Criteria in Solid Tumors (RECIST) which is based on radiological measurements of lesion size.
The difficulty in evaluating cell trafficking and distribution of transferred cells in vivo is one of the major concerns in adoptive therapy. Radioisotope cell labeling is the most common method used to study the distributions of cells in vivo. 18F-2-fluoro-2-deoxy-D-glucose ([18F]FDG) has been extensively used as a parameter of glucose metabolism in various cells allowing in vivo visualization of cells and tissues by Positron Emission Tomography (PET) [3]. Labeling studies of blood components demonstrate that erythrocytes and leukocytes incorporate and maintain [18F]FDG for several hours.